JP4039343B2 - Evaporative fuel processing device for internal combustion engine - Google Patents

Description

  The present invention relates to an evaporated fuel processing apparatus for an internal combustion engine, and more particularly to an evaporated fuel processing apparatus for an internal combustion engine that supplies the evaporated fuel as a starting fuel when the internal combustion engine is started.

  Conventionally, for example, Patent Document 1 describes a technique in which when an internal combustion engine is started, fuel vapor (evaporated fuel) adsorbed by a canister is discharged and supplied to a surge tank, and supplied into a combustion chamber together with fresh air. . Since the wall surface temperature does not rise at the time of starting the internal combustion engine and immediately after the start, the fuel injected from the fuel injection valve is difficult to vaporize and it is difficult to realize stable combustion. On the other hand, since the fuel vapor is already completely gasified fuel, it has excellent ignitability. Therefore, when the fuel vapor is used as the starting fuel for the internal combustion engine, the startability of the internal combustion engine can be improved.

Patent Document 2 discloses a technique in which a fuel tank and an intake pipe are connected by an evaporated fuel passage and fuel vapor in the fuel tank is directly supplied to the intake pipe. In this technique, the inside of the fuel tank is always maintained at a negative pressure. As a means for this, the opening of a control valve provided in the evaporated fuel passage is controlled according to the internal pressure in the fuel tank, and the fuel is The fuel vapor in the tank is extracted to the intake pipe.
JP 11-280532 A Japanese Patent Laid-Open No. 11-36937

  However, it is difficult to adjust the fuel injection amount to be injected from the fuel injection valve with the technique of the above-mentioned Patent Document 1. The amount of fuel vapor released from the canister depends on the amount of fuel vapor adsorbed by the canister, so only very low concentration fuel vapor may be supplied, or very dense fuel vapor is supplied. There is also. For this reason, it is necessary to control the fuel injection amount from the fuel injection valve according to the estimated value by estimating the evaporated fuel adsorption amount of the canister. In the technique of Patent Document 1, the amount of evaporated fuel adsorption is estimated based on the learned value of the air-fuel ratio feedback correction coefficient. When the internal combustion engine is started, the evaporated fuel adsorption is based on the learned value obtained by the feedback control at the previous operation. The amount is estimated. However, when the internal combustion engine is stopped, fuel vapor may be adsorbed or released from the canister. For this reason, there may be a large difference between the evaporated fuel adsorption amount estimated from the previous learning value and the actual evaporated fuel adsorption amount. In such a situation, even if the fuel injection amount of the fuel injection valve is determined based on the evaporated fuel adsorption amount estimated from the previous learning value, a desired amount of fuel cannot be supplied, which may hinder the combustion state. There is a risk of coming. Although it is possible to measure the concentration of fuel vapor using a sensor, an extra cost is required.

  On the other hand, when the fuel vapor in the fuel tank is supplied to the intake pipe as in the technique of Patent Document 2, the concentration of the fuel vapor is always expected to be a certain level compared to the concentration of the fuel vapor released from the canister. Can do. However, since the technique of Patent Document 2 releases the fuel vapor to the intake pipe in order to always maintain the internal pressure in the fuel tank at a negative pressure, the internal pressure in the fuel tank has already become a negative pressure. If a negative pressure occurs during the operation, a sufficient amount of fuel vapor cannot be supplied.

  The present invention has been made to solve the above-described problems, and provides an evaporative fuel processing apparatus capable of improving startability of an internal combustion engine by supplying fuel vapor having a stable concentration when the internal combustion engine is started. The purpose is to provide.

In order to achieve the above object, a first invention is an evaporated fuel processing apparatus for an internal combustion engine,
A fuel tank for storing fuel;
An air inlet for communicating the fuel tank with the outside world and maintaining the inside of the fuel tank from approximately atmospheric pressure to positive pressure;
Evaporative fuel supply means for communicating the fuel tank to the intake passage and supplying the evaporated fuel in the fuel tank to the intake passage when starting the internal combustion engine;
It is characterized by having.

  Further, according to a second invention, in the first invention, a canister that adsorbs the evaporated fuel generated in the fuel tank is provided at the atmosphere introduction port, and the fuel tank communicates with the outside through the canister. It is characterized by being.

  According to a third aspect of the present invention, in the first or second aspect, the supply of the evaporated fuel from the fuel tank to the intake passage is stopped when a predetermined operating condition is satisfied after the internal combustion engine is started. It is characterized by.

Further, a fourth invention comprises the canister for adsorbing the evaporated fuel generated in the fuel tank in the third invention,
The evaporated fuel supply means supplies the evaporated fuel discharged from the canister to the front air intake passage after the supply of the evaporated fuel from the fuel tank to the intake passage is stopped.

  In a fifth aspect based on the fourth aspect, the evaporated fuel supply means is configured to supply the evaporated fuel discharged from the canister after a predetermined time has elapsed after the supply of evaporated fuel from the fuel tank to the intake passage is stopped. It is characterized by being supplied to the front air intake passage.

  According to a sixth aspect, in the fifth aspect, the predetermined time is a time until the evaporated fuel supplied from the fuel tank to the intake passage is sucked into the combustion chamber.

According to a seventh invention, in any one of the first to sixth inventions, the evaporated fuel supply means includes an evaporated fuel passage connected to the intake passage, and a control valve disposed in the evaporated fuel passage. Including
When the internal combustion engine is stopped, the control valve is closed while the evaporated fuel passage is in communication with the fuel tank.

According to an eighth aspect of the present invention, in any one of the fourth to sixth aspects, the evaporated fuel supply means includes an evaporated fuel passage connected to the intake passage, a control valve disposed in the evaporated fuel passage, Connection switching means for selectively connecting one of the canister and the fuel tank to the evaporated fuel passage,
When the IG switch of the internal combustion engine is turned off, the connection switching means switches the connection to the evaporated fuel passage from the canister to the fuel tank, and the evaporated fuel passage is filled with evaporated fuel generated in the fuel tank. The control valve is closed when the evaporated fuel passage is in communication with the fuel tank at the time when it is estimated that the fuel tank has been closed.

  According to the first invention, the inside of the fuel tank is maintained from substantially atmospheric pressure to a positive pressure by communication with the outside through the air introduction port, so that the inside of the fuel tank does not become a negative pressure more than the intake passage. Evaporated fuel can be supplied as needed. Therefore, according to the present invention, the fuel injection amount can be set to an appropriate value by supplying the evaporated fuel in the fuel tank that can always be expected to have a certain concentration at the start of the internal combustion engine where the combustion becomes unstable. Combustion stability can be improved.

  According to the second invention, when the atmosphere is introduced into the fuel tank from the outside through the atmosphere introduction port, the evaporated fuel adsorbed in the canister is released into the fuel tank. The adsorption force can be ensured. Even if the concentration of the evaporated fuel discharged from the canister and the concentration of the evaporated fuel in the fuel tank at this time are different, the fuel tank serves as a buffer, so that the evaporated fuel supplied from the fuel tank to the intake passage There is no significant change in concentration.

  According to the third aspect, by stopping the supply of the evaporated fuel from the fuel tank to the intake passage when a predetermined operating condition is satisfied, the evaporated fuel to be supplied at the next start is secured in the fuel tank. Can do. Preferably, the predetermined operating condition is that the intake port is warmed up and / or that the catalyst device provided in the exhaust passage is warmed up to an active state. When the intake port is warmed up, the fuel does not adhere to the wall surface in a liquid state, so that good combustion can be obtained with the injected fuel from the fuel injection valve without supplying the evaporated fuel. Moreover, even if unburned HC is generated after the catalytic device is activated, it can be purified by the catalyst.

  According to the fourth invention, after the supply of the evaporated fuel from the fuel tank to the intake passage is stopped, the evaporated fuel discharged from the canister is supplied to the intake passage, thereby purging the canister and ensuring the adsorption power of the canister. can do.

  According to the fifth aspect of the present invention, the evaporation fuel discharged from the canister is supplied to the intake passage not immediately after the supply of the evaporated fuel from the fuel tank to the intake passage but after the elapse of a predetermined time. It is possible to prevent the air-fuel ratio feedback control from being hindered by a sudden change in the fuel concentration.

  According to the sixth aspect of the present invention, the predetermined time is set to the time until the evaporated fuel supplied from the fuel tank to the intake passage is sucked into the combustion chamber, thereby releasing the evaporated fuel from the fuel tank and the canister. The canister can be quickly purged to ensure the adsorption power of the canister while preventing the evaporated fuel from continuing in the intake passage.

  According to the seventh aspect, since the internal combustion engine is started in a state where the evaporated fuel passage is filled with the evaporated fuel, it becomes possible to quickly supply the evaporated fuel to the internal combustion engine at the time of starting. The startability can be further improved.

  According to the eighth aspect of the invention, it is possible to quickly supply the evaporated fuel to the internal combustion engine at the next start without leaving the concentrated evaporated fuel in the fuel tank wastefully in the intake passage. Can be further improved.

Embodiment 1 FIG.
The first embodiment of the present invention will be described below with reference to FIGS.
FIG. 1 is a diagram for explaining the outline of the evaporated fuel processing apparatus according to Embodiment 1 of the present invention. The evaporated fuel processing apparatus of this embodiment includes a fuel tank 10. The fuel tank 10 is provided with a tank internal pressure sensor 12 for measuring the tank internal pressure. The tank internal pressure sensor 12 is a sensor that detects a tank internal pressure as a relative pressure to the atmospheric pressure and generates an output corresponding to the detected value.

  The fuel tank 10 is formed with a protruding portion 11 protruding into the fuel tank from the ceiling surface, and a vapor passage (evaporated fuel passage) 20 is connected to the protruding portion 11. The vapor passage 20 is a passage for extracting fuel vapor (evaporated fuel) generated in the fuel tank 10 to the outside, and is connected to an intake passage 32 of the internal combustion engine 30. The vapor passage 20 is provided with a purge valve (D-VSV: Duty-Vacuum Switching Valve) 28 for controlling the flow rate of the gas flowing through the vapor passage 20. The purge valve 28 is a control valve that realizes an opening substantially corresponding to the duty ratio by being driven by a duty signal.

  An air inlet 14 is formed in the fuel tank 10. A canister 22 whose one end is open to the outside world is connected to the air introduction port 14, and the fuel tank 10 communicates with the outside world via the canister 22. The canister 22 is filled with activated carbon for adsorbing fuel vapor. Although a slight pressure loss (approximately several kilopascals) occurs due to the canister 22 being interposed, even when the fuel vapor is extracted from the fuel tank 10, the fuel tank is introduced by the introduction of the atmosphere from the atmosphere introduction port 14. 10 is maintained at least at substantially atmospheric pressure. Note that the air introduction port 14 is provided apart from the above-described protruding portion 11 so that the purge gas flowing into the fuel tank 10 from the canister 22 does not flow into the vapor passage 20 as it is.

  A throttle valve 38 for controlling the intake air amount is disposed in the intake passage 32 of the internal combustion engine 30, and a surge tank 34 that is a volume portion is formed downstream of the throttle valve 38 in the intake passage 32. The above-described vapor passage 20 communicates with the upstream portion of the surge tank 34. An intake manifold 36 is connected to the surge tank 34, and the intake manifold 36 is electrically connected to each intake port 40 of the internal combustion engine 30. A fuel injection valve 44 for injecting fuel into each cylinder is disposed in the vicinity of the intake port 40. The internal combustion engine 30 incorporates a rotation speed sensor 46 that detects the engine speed and a cooling water temperature sensor 47 that detects the cooling water temperature. Further, an air flow meter 45 for detecting the intake air amount is provided upstream of the throttle valve 38 in the intake passage 32, and a catalyst device (not shown) for purifying harmful components in the exhaust gas is provided in the exhaust passage (not shown). An oxygen concentration sensor 48 for detecting the oxygen concentration in the exhaust gas is provided.

  The evaporated fuel processing apparatus shown in FIG. 1 includes an ECU (Electronic Control Unit) 50. The ECU 50 is a control device for the evaporated fuel processing apparatus, and receives output signals from the various sensors described above and supplies drive signals to various actuators. In the present embodiment, in particular, drive signals are supplied to the purge valve 28 and the fuel injection valve 44. Hereinafter, the control of the purge valve 28 performed by the ECU 50 will be described with reference to the flowchart shown in FIG. The control of the fuel injection valve 44 performed by the ECU 50 will be described with reference to the flowchart shown in FIG.

  FIG. 2 is a flowchart for explaining a flow of purge control executed by the ECU 50 as a control device of the evaporated fuel processing device in the present embodiment. In the routine shown in FIG. 2, first, the engine speed NE is detected based on the output of the speed sensor 46, and is compared with a predetermined determination value KNE (step 100). The determination value KNE is a rotation speed at which it can be estimated that the internal combustion engine 30 has started, and is set to about the start rotation speed by the starter (for example, 50 rpm).

  As a result of the comparison, if the engine speed NE is equal to or less than the determination value KNE, the internal combustion engine 30 has not yet been started, so the fuel vapor is not released and the purge valve 28 remains closed (step 102). ).

  When the engine speed NE exceeds the determination value KNE, the purge valve 28 is opened and the fuel vapor is released (step 104). By opening the purge valve 28, the fuel tank 10 and the intake passage 32 are in communication with each other. Since the fuel tank 10 has a substantially atmospheric pressure and the intake passage 32 has a negative pressure, the fuel vapor in the fuel tank 10 passes through the vapor passage 20 and is sucked into the intake passage 32. The fuel vapor is supplied to the surge tank 34 together with fresh air introduced through the throttle valve 38, and is supplied to the combustion chamber of each cylinder together with the fuel injected from the fuel injection valve 44. The opening degree of the purge valve 28 is set to fully open so as to supply as much fuel vapor as possible to the internal combustion engine 30 as starting fuel. While the purge valve 28 is open, fuel vapor continues to be sucked out of the fuel tank 10. However, since the fuel tank 10 is also communicated with the outside through the atmosphere introduction port 14, The internal pressure will not drop. That is, the flow rate of the fuel vapor does not decrease due to a decrease in the internal pressure in the fuel tank 10.

  Further, since the canister 22 is disposed at the atmosphere introduction port 14, when the atmosphere (fresh air) is introduced into the fuel tank 10 from the atmosphere introduction port 14, the fuel vapor adsorbed on the canister 22 together with the atmosphere Desorbed and flows into the fuel tank 10. As a result, the canister 22 is purged and its adsorption force is ensured. At this time, the fuel vapor discharged from the canister 22 is likely to have a concentration different from that of the fuel vapor in the fuel tank 10, but the fuel tank 10 has an extremely large volume compared to the canister 22, and the fuel tank 10 Acts as a buffer. Therefore, even if the fuel vapor adsorbed by the canister 22 flows into the fuel tank 10, the concentration of the fuel vapor supplied from the fuel tank 10 to the intake passage 32 does not change greatly.

  According to the purge control routine described above, the rich fuel vapor in the fuel tank 10 can be supplied to the internal combustion engine 30 from the start of the internal combustion engine 30. As described above, the fuel vapor is superior in ignitability compared to the atomized fuel injected from the fuel injection valve 44 and easily combusts. Therefore, the internal combustion engine 30 can be started by supplying the fuel vapor as the starting fuel. Can be improved. Further, since the fuel vapor is a relatively light component, the concentration of HC contained in the unburned gas is also low.

  Further, the fuel vapor in the fuel tank 10 can always be expected to have a certain concentration even when the internal combustion engine 30 is started, unlike the fuel vapor discharged from the canister 22. In order to achieve an appropriate air-fuel ratio, it is necessary to reduce the fuel injection amount from the fuel injection valve 44 in accordance with the fuel vapor supply amount. In this way, the fuel vapor concentration can be expected to some extent, The fuel injection amount from the fuel injection valve 44 can be accurately obtained.

The fuel injection amount from the fuel injection valve 44 is determined by the fuel injection time TAU that is the valve opening time of the fuel injection valve 44. The fuel injection time TAU is calculated by the following equation (1).
TAU = TP × (FW + FAF + KGX−FPG) (1)
In the above equation (1), TP is the basic fuel injection time, and is calculated by multiplying the ratio (GA / NE) between the engine speed NE and the intake air amount GA by a predetermined injection coefficient K.
In the above equation (1), FW, FAF, KGX, and FPG are correction coefficients. Among these, FW is a water temperature correction coefficient, and is set according to the cooling water temperature of the internal combustion engine 30. FAF is an air-fuel ratio feedback coefficient. When the exhaust air-fuel ratio detected based on the output of the oxygen concentration sensor 48 is rich, it is set to a small value to shorten the fuel injection time TAU, and the exhaust air-fuel ratio becomes lean. Is set to a large value to extend the fuel injection time TAU. KGX is a learning value for absorbing the deviation of the air-fuel ratio due to the influence of secular change or the like, and is set for each operation region divided by the engine speed and the engine load. FPG is a purge correction coefficient for reducing and correcting the fuel injection amount in accordance with the supply amount of fuel vapor (purge gas).

  The above-described fuel injection time TAU is calculated according to the routine shown in the flowchart of FIG. 3 by the ECU 50 as a control device of the evaporated fuel processing device. In the routine shown in FIG. 3, it is first determined whether the purge valve 28 is currently open (step 110).

  If the purge valve 28 is not opened as a result of the determination, no fuel vapor is supplied to the internal combustion engine 30, so the purge correction coefficient FPG is set to zero (step 112).

On the other hand, if the purge valve 28 is open in the determination of step 110, the purge correction coefficient FPG is set to a value obtained by the following equation (2) (step 114).
FPG = FTNK × PGR (2)
In the above equation (2), FTNK is a coefficient determined by the vapor concentration in the fuel tank 10. Since the vapor concentration in the fuel tank 10 is stable and is always expected to be a certain level, the vapor concentration coefficient FTNK is fixed to a representative value corresponding to the vapor concentration at the normally estimated pressure and temperature. Yes.
In the above equation (2), PGR is the current purge rate. The purge rate PGR is a value indicating the ratio (QPG / GA) between the intake air amount GA and the flow rate QPG of the purge gas flowing through the purge valve 28 as a percentage. Here, the purge flow rate QPG can be obtained by a known method based on the intake pressure PM and the drive duty ratio of the purge valve 28. The intake pressure PM can be estimated by a known method based on the intake air amount GA and the like. Here, the purge rate PGR is set with the purge valve 28 fully opened, that is, the drive duty ratio is set to 100%.

  In the routine shown in FIG. 3, next, based on the purge correction coefficient FPG set in step 112 or step 114, the fuel injection time TAU is calculated according to the above equation (1) (step 116). As a result, the fuel injection time TAU is corrected to decrease in accordance with the amount of fuel vapor supplied from the fuel tank 10 to the internal combustion engine 30.

  According to the fuel injection time calculation routine described above, when fuel vapor is supplied from the fuel tank 10 to the internal combustion engine 30 when the internal combustion engine 30 is started, the fuel injection time TAU is corrected according to the supply amount. be able to. Since the concentration of the fuel vapor in the fuel tank 10 can always be expected to a certain level, the error between the above-described representative value and the actual value is small, and the fuel injection time TAU calculated using the above-described representative value greatly deviates from the appropriate value. There is nothing. Therefore, according to the evaporated fuel processing apparatus of the present embodiment, the fuel injection valve 44 supplies the evaporated fuel in the fuel tank 10 that can always be expected to have a certain concentration when starting the internal combustion engine 30 where the combustion becomes unstable. The fuel injection amount can be set to an appropriate value, and good combustion stability can be obtained from the start.

  In the first embodiment described above, the “evaporated fuel supply means” of the first invention is realized by the vapor passage 20, the purge valve 28, and the ECU 50 that executes the routine of FIG. Further, in the first embodiment described above, the end timing of the supply of fuel vapor from the fuel tank 10, that is, the closing timing of the purge valve 28 is not particularly defined. As for the closing timing of the purge valve 28, a suitable timing will be described in an embodiment described later. For example, an appropriate purge valve opening time (for example, 20 sec) is determined, and the count value of the timer is set to the purge valve opening time. The purge valve 28 may be closed after elapse of time. In the first embodiment, the vapor concentration coefficient FTNK is fixed to the representative value. However, the internal pressure and temperature in the fuel tank 10 may be measured and set to values according to the measured values. .

Embodiment 2.
Hereinafter, the second embodiment of the present invention will be described with reference to FIGS.
FIG. 4A is a view for explaining an outline of the evaporated fuel processing apparatus according to the second embodiment of the present invention. In FIG. 4 (a), parts common to those in the first embodiment are given the same reference numerals, and redundant descriptions thereof are omitted.

  As shown in FIG. 4A, the present embodiment is different from the first embodiment in the flow path of the fuel vapor discharged from the canister 22. That is, the canister 22 is connected not only to the air inlet 14 of the fuel tank 10 but also directly to the vapor passage 20 as in the first embodiment. In the present embodiment, the vapor passage 20 includes a main line 20a, a tank line 20b branched from the main line 20a, and a canister line 20c. The main line 20a is in the intake passage 32, the tank line 20b is in the fuel tank 10, and the canister Line 20 c is connected to canister 22. Thereby, in this embodiment, it is possible to supply either the fuel vapor in the fuel tank 10 or the fuel vapor discharged from the canister 22 directly to the intake passage 32 by sharing the single main line 20a. It has become.

  A switching valve 26 is disposed at a branching portion of the vapor passage 20 between the main line 20a, the tank line 20b, and the canister line 20c. The switching valve 26 is a valve that selectively switches the connection state of the tank line 20b and the canister line 20c to the main line 20a, and one of the lines 20b and 20c is connected to the main line 20a by the operation of the switching valve 26. It has come to be. Here, it is assumed that when the canister line 20c is connected to the main line 20a, the switching valve 26 is “ON”, and when the tank line 20b is connected to the main line 20a, the switching valve 26 is “OFF”. To do. Here, the OFF state is the basic state of the switching valve 26. The switching valve 26 switches the connection state of the vapor passage 20 according to a drive signal supplied from the ECU 50.

  When the switching valve 26 is off, the fuel tank 10 is connected to the intake passage 32, and the fuel vapor in the fuel tank 10 is supplied to the intake passage 32. At this time, the fuel vapor discharged from the canister 22 is supplied into the fuel tank 10 from the air introduction port 14. On the other hand, when the switching valve 26 is on, the canister 22 is connected to the intake passage 32, and the fuel vapor discharged from the canister 22 is directly supplied to the intake passage 32.

  In the present embodiment, the ECU 50 as a control device of the evaporated fuel processing device supplies drive signals to the purge valve 28, the fuel injection valve 44, and the switching valve 26. Hereinafter, the control of the purge valve 28 and the switching valve 26 performed by the ECU 50 will be described with reference to the flowchart shown in FIG. The control of the fuel injection valve 44 performed by the ECU 50 will be described with reference to the flowchart shown in FIG. In the following description, parameters that are the same as those in the first embodiment are given the same symbols, and redundant descriptions thereof are omitted.

  FIG. 5 is a flowchart for explaining a flow of purge control executed by the ECU 50 as a control device of the evaporated fuel processing device in the present embodiment. In the routine shown in FIG. 5, first, the engine speed NE is detected based on the output of the speed sensor 46, and is compared with a predetermined determination value KNE (step 120).

  As a result of the comparison, when the engine speed NE is equal to or smaller than the determination value KNE, the switching valve 26 is maintained in the basic state, that is, the off state (step 122). Further, the purge valve 28 is kept closed (step 124).

  If the engine speed NE exceeds the determination value KNE, then the coolant temperature THW of the internal combustion engine 30 is detected based on the output of the coolant temperature sensor 47 and compared with a predetermined determination value KTHW (step 126). . The determination value KTHW is a reference value for determining whether or not the current start is a cold start. For example, the determination value KTHW may be set to the lowest cooling water temperature at which the internal combustion engine 30 can maintain a stable idling state. Specific values can be appropriately determined by experiments.

  As a result of the comparison, if the coolant temperature THW is equal to or lower than the determination value KTHW, the switching valve 26 is maintained in the basic state of OFF (step 128). On the other hand, the purge valve 28 is opened fully (step 130). By opening the purge valve 28 while the switching valve 26 is off, the fuel tank 10 and the intake passage 32 are in communication with each other. Thereby, the fuel vapor in the fuel tank 10 is supplied to the internal combustion engine 30.

  When the coolant temperature THW exceeds the determination value KTHW, the switching valve 26 is turned on, and the canister 22 and the intake passage 32 are brought into communication (step 132). The control of the purge valve 28 is switched from the start-time control in which the drive duty ratio is 100% to the normal purge control (step 134). The normal purge control here is a control in which a target purge rate is set based on the operating state of the internal combustion engine 30, and the drive duty ratio of the purge valve 28 is set so that the purge rate PGR becomes the set target purge rate. That is. Since such normal purge control is known, detailed description thereof is omitted here.

  According to the purge control routine described above, when the internal combustion engine 30 has already been warmed up, as in the case of restarting immediately after stopping, the normal purge control is immediately started and the purge gas from the canister 22 is started. Is supplied to the internal combustion engine 30. Only when the internal combustion engine 30 is cold-started, the rich fuel vapor in the fuel tank 10 is supplied to the internal combustion engine 30, and after the internal combustion engine 30 is warmed up, the internal combustion engine 30 is transferred from the fuel tank 10 to the canister 22. The fuel vapor supply source is switched. Since the concentration of the fuel vapor discharged from the canister 22 by the purge is unknown, a large amount of fuel vapor cannot be supplied until the concentration learning is performed. If the fuel vapor adsorption amount is small in the first place, the concentration is high. Fuel vapor cannot be supplied. However, after the internal combustion engine 30 is warmed up, good combustion can be obtained with the fuel injected from the fuel injection valve 44 without depending on the supply of fuel vapor. The purge control routine of the present embodiment is such that the fuel vapor in the fuel tank 10 having a stable concentration is supplied only when the catalyst device is inactive and cold start, and the fuel vapor in the fuel tank 10 is supplied. By limiting to the cold start, it is possible to prevent the fuel vapor in the fuel tank 10 from being wasted and withered.

  Further, while the inside of the fuel tank 10 is maintained at substantially atmospheric pressure, the inside of the intake passage 32 has a negative pressure, so that the canister 22 is directly connected to the intake passage 32 after the internal combustion engine 30 is warmed up. Thus, the fuel vapor adsorbed on the canister 22 is efficiently purged. That is, according to the evaporated fuel processing apparatus of the present embodiment, the purge efficiency of the canister 22 can be increased as compared with the first embodiment, and the adsorption power of the canister can be further ensured.

  In the present embodiment, the calculation of the fuel injection time TAU is executed by a routine shown in FIG. 6 so as to correspond to the above-described purge control routine by the ECU 50 as a control device of the evaporated fuel processing device. In the routine shown in FIG. 6, it is first determined whether the purge valve 28 is currently open (step 140).

  When the purge valve 28 is not opened, no fuel vapor is supplied to the internal combustion engine 30, and therefore the purge correction coefficient FPG in the above equation (1) is set to zero. (Step 142)

  If the purge valve 28 is open in the determination in step 140, it is next determined whether the switching valve 26 is on or off, that is, which of the fuel tank 10 and the canister 22 is connected to the intake passage 32. (Step 144).

  As a result of the determination in step 144, when the switching valve 26 is off and the fuel tank 10 is connected to the intake passage 32, the purge correction coefficient FPG is set to a value determined by the above-described equation (2) ( Step 146).

On the other hand, when the switching valve 26 is turned on in the determination of step 144 and the canister 22 is connected to the intake passage 32, the purge correction coefficient FPG is set to a value obtained by the following equation (3) (step 148). ).
FPG = FGPG × PGR (3)
In the above equation (3), FGPG is a vapor concentration learning coefficient, which is a learned value of the vapor concentration of the fuel vapor discharged from the canister 22. The vapor concentration learning coefficient FGPG is appropriately updated so that the vibration center of the air-fuel ratio feedback coefficient FAF approaches the reference value during execution of normal purge control. For example, when the vibration center of the air-fuel ratio feedback coefficient FAF is biased to the rich side during the purge control, the vapor concentration learning coefficient FGPG is updated to a larger value so as to change the exhaust air-fuel ratio to the lean side. .
Note that the initial value of the vapor concentration learning coefficient FGPG at the start of this time is the value of the vapor concentration learning coefficient FGPG at the previous stop of operation. Since the vapor is adsorbed or released in the canister 22 even when the operation is stopped or the learning of the vapor concentration learning coefficient FGPG after the start is not performed, the vapor concentration learning coefficient is immediately after the switching of the switching valve 26. There is also a possibility that FGPG is largely deviated from the actual value. However, while the routine shown in FIG. 6 is repeated, the vapor concentration learning coefficient FGPG is updated to a value that matches the actual value.

  In the routine shown in FIG. 6, next, based on the purge correction coefficient FPG set in step 142, step 146 or step 148, the fuel injection time TAU is calculated according to the above equation (1) (step 150). As a result, the fuel injection time TAU is corrected to decrease in accordance with the amount of fuel vapor supplied from the fuel tank 10 or the canister 22 to the internal combustion engine 30.

  According to the fuel injection time calculation routine described above, when fuel vapor is supplied from the fuel tank 10 to the internal combustion engine 30 when the internal combustion engine 30 is started, the fuel injection time TAU is corrected according to the supply amount. be able to. In addition, after the internal combustion engine 30 is warmed up and the connection to the intake passage 32 is switched from the fuel tank 10 to the canister 22 by the operation of the switching valve 26, the amount of fuel vapor discharged from the canister 22 is increased. The fuel injection time TAU can be corrected. Therefore, according to the evaporated fuel processing apparatus of the present embodiment, when the internal combustion engine 30 where the combustion becomes unstable is cold started, the fuel injection valve is always supplied while supplying the evaporated fuel in the fuel tank 10 that can be expected to have a certain concentration. The fuel injection amount from 44 can be set to an appropriate value, and good combustion stability can be obtained from the start. Further, after the internal combustion engine 30 is sufficiently warmed up, the fuel injection amount from the fuel injection valve 44 can be set to an appropriate value by learning the vapor concentration learning coefficient FGPG, and good combustion stability is maintained. can do.

  By the way, the evaporative fuel processing apparatus of this embodiment is not limited to the structure shown to Fig.4 (a), It can also take a structure as shown in FIG.4 (b). In FIG. 4 (b), parts common to those shown in FIG. 4 (a) are given the same reference numerals. The configuration shown in FIG. 4B is characterized in that the switching valve 26 is arranged inside the canister 22. In this configuration, the canister line 20 c in FIG. 4A is omitted, and the fuel vapor discharged from the canister 22 directly enters the switching valve 26. Further, a passage 18 for connecting the switching valve 26 and the inside of the fuel tank 10 is provided in the atmosphere introduction port 14 of the fuel tank 10 to which the canister 22 is connected. This passage 18 is shown in FIG. This corresponds to the tank line 20b. According to the evaporative fuel processing apparatus having such a configuration, it is possible to reduce the number of connecting portions exposed to the outside, so that there are few open portions of the fuel vapor and the possibility of the fuel vapor leaking into the atmosphere can be reduced. it can.

  In the second embodiment described above, the “evaporated fuel supply means” of the third invention is realized by the vapor passage 20, the purge valve 28, the switching valve 26, and the ECU 50 that executes the routine of FIG.

Embodiment 3.
Hereinafter, Embodiment 3 of the present invention will be described with reference to FIG.
The fuel vapor processing apparatus according to the present embodiment can be realized by causing the ECU 50 to execute the routine of FIG. 7 instead of the routine of FIG. 5 in the second embodiment.

  In the second embodiment described above, the coolant temperature THW is detected and compared with the determination value KTHW. The reason for detecting the coolant temperature THW is to indirectly determine whether the wall surface temperature of the internal combustion engine 30, particularly the wall surface temperature of the intake port 40 into which the fuel is injected, has risen to the extent that the fuel is vaporized. If the wall surface temperature of the internal combustion engine 30 is sufficiently high, good combustion can be obtained even with the injected fuel. Therefore, the generation of unburned HC can be suppressed without supplying the fuel vapor of the fuel tank 10. On the other hand, a catalyst device is arranged in the exhaust passage. If this catalyst device is warmed up and activated, even if unburned HC is generated due to poor combustion, it is a catalyst device. Can be purified. Therefore, in the present embodiment, in addition to the wall surface temperature becoming high, the catalyst device being warmed up is also used as one of the determination conditions in the purge control. The wall surface temperature can be estimated from the history of the operating state of the internal combustion engine 30 (engine speed, engine load, etc.) in addition to the coolant temperature THW. The catalyst temperature can be estimated from the total amount of exhaust gas flowing into the catalyst device after the internal combustion engine 30 is started. Since the total amount of exhaust gas is substantially equal to the total amount of intake air, the catalyst temperature can be estimated by calculating the total amount of intake air after startup.

  FIG. 7 is a flowchart for explaining the flow of purge control executed by the ECU 50 as the control device of the evaporated fuel processing device in the present embodiment. In the routine shown in FIG. 7, first, the engine speed NE is detected based on the output of the speed sensor 46, and is compared with the determination value KNE (step 160).

  As a result of the comparison, when the engine speed NE is equal to or less than the determination value KNE, the switching valve 26 is maintained in the basic state, that is, the off state (step 162). Further, the purge valve 28 is kept closed (step 164).

  If engine speed NE exceeds determination value KNE, it is next determined whether or not the wall surface has become sufficiently hot, that is, whether or not the wall surface temperature has exceeded a predetermined determination value (step 166). The wall surface temperature is an estimated value from the cooling water temperature THW and the operating state of the internal combustion engine 30 as described above. If the result of determination is that the wall surface is sufficiently hot, the switching valve 26 is turned on, and the canister 22 and the intake passage 32 are brought into communication (step 174). Then, the control of the purge valve 28 is switched from the startup control in which the drive duty ratio is 100% to the normal purge control (step 176).

  If the result of determination in step 166 is that the wall surface is not sufficiently hot, it is determined whether the catalyst device has been warmed up, that is, whether the catalyst temperature has exceeded a predetermined determination value (step 168). The catalyst temperature is an estimated value from the intake air amount as described above. As a result of the determination, if it is determined that the catalyst device is warmed up, the switching valve 26 is turned on and the canister 22 and the intake passage 32 are brought into communication even if the wall surface is not sufficiently heated. (Step 174). Then, the control of the purge valve 28 is switched from the startup control in which the drive duty ratio is 100% to the normal purge control (step 176).

  On the other hand, as a result of the determination in step 166 and step 168, when it is determined that the wall surface is not sufficiently heated and the catalyst device is not warmed up, the switching valve 26 is off in the basic state. (Step 170). On the other hand, the purge valve 28 is opened to the fully open state (step 172).

  According to the purge control routine described above, unburned HC can be purified not only when the wall surface temperature rises to such an extent that the fuel injected from the fuel injection valve 44 can be vaporized but also when the wall surface temperature does not rise. When the catalyst device is warmed up to the extent, the fuel vapor supply source to the internal combustion engine 30 is switched from the fuel tank 10 to the canister 22. That is, the fuel vapor is supplied from the fuel tank 10 only in a situation where unburned HC can be released to the atmosphere. Therefore, according to the evaporated fuel processing apparatus of the present embodiment, the fuel vapor in the fuel tank 10 can be used effectively without being wasted.

  In the third embodiment described above, the “evaporated fuel supply means” of the third aspect of the invention is realized by the vapor passage 20, the purge valve 28, the switching valve 26, and the ECU 50 that executes the routine of FIG.

Embodiment 4.
Hereinafter, Embodiment 3 of the present invention will be described with reference to FIGS.
The fuel vapor processing apparatus of the present embodiment can be realized by causing the ECU 50 to execute the routine of FIG. 8 instead of the routine of FIG. 5 in the second embodiment.

  In the above-described second embodiment, when the coolant temperature THW exceeds the determination value KTHW, the fuel vapor supply source to the internal combustion engine 30 is switched from the fuel tank 10 to the canister 22 to start normal vapor control. . However, even after the switching valve 26 is switched, the thick fuel vapor supplied from the fuel tank 10 remains in the surge tank 34 for a while. For this reason, the fuel vapor from the fuel tank 10 and the fuel vapor from the canister 22 coexist in the surge tank 34, and the vapor concentration changes suddenly at the boundary. The air-fuel ratio feedback control is performed while learning the vapor concentration using the vapor concentration learning coefficient FGPG. However, when the vapor concentration suddenly changes in this way, the feedback is not in time, and the air-fuel ratio may be greatly disturbed. Therefore, in this embodiment, the purge control is executed according to the routine of FIG. 8 to prevent the air-fuel ratio from being disturbed due to switching.

  FIG. 8 is a flowchart for explaining the flow of purge control executed by the ECU 50 as the control device of the evaporated fuel processing device in the present embodiment. In the routine shown in FIG. 8, first, the engine rotational speed NE is detected based on the output of the rotational speed sensor 46 and compared with the determination value KNE (step 180).

  As a result of the comparison, when the engine speed NE is equal to or smaller than the determination value KNE, the switching valve 26 is maintained in the basic state, that is, the off state (step 182). Further, the purge valve 28 is kept closed (step 184). Here, FIG. 9 is a diagram showing changes in the on / off state of the switching valve 26 and changes in the purge rate PGR when the routine of FIG. 8 is executed in correspondence with changes in the coolant temperature THW and the engine speed NE over time. is there. A section A in FIG. 9 shows each state until the determination condition of step 180 is satisfied.

  If the engine speed NE exceeds the determination value KNE, next, the coolant temperature THW of the internal combustion engine 30 is detected based on the output of the coolant temperature sensor 47, and compared with a predetermined first determination value KTHW (step). 186).

  As a result of the comparison, when the coolant temperature THW is equal to or lower than the first determination value KTHW, the switching valve 26 is maintained in the OFF state, which is the basic state (step 188). On the other hand, the purge valve 28 is opened to the fully open state (step 190). The on / off state of the switching valve 26 and the purge rate PGR from the satisfaction of the determination condition of step 180 to the satisfaction of the determination condition of step 186 are indicated by a section B in FIG.

  When the coolant temperature THW exceeds the first determination value KTHW, the coolant temperature THW is further compared with a predetermined second determination value KTHW + A (step 192). The second determination value KTHW + A is larger than the first determination value KTHW, and the purge valve 28 is once fully closed until the cooling water temperature THW exceeds the second determination value KTHW + A (step 184). The on / off state of the switching valve 26 and the purge rate PGR of the purge valve 28 from the satisfaction of the determination condition of Step 190 to the satisfaction of the determination condition of Step 192 are indicated by a section C in FIG. When the purge valve 28 is fully closed, supply of new fuel vapor into the intake passage 32 is eliminated, and the rich fuel vapor accumulated in the surge tank 34 gradually decreases.

  The temperature difference A between the above two determination values is the time until the fuel vapor supplied from the fuel tank 10 to the intake passage 32 is taken into the combustion chamber of the internal combustion engine 30. In other words, the fuel tank It is set in consideration of the time until the rich fuel vapor supplied from 10 disappears from the surge tank 34, or the time until it becomes sufficiently small. By setting the temperature difference A in consideration of such time, the canister 22 can be purged while preventing the fuel vapor from the fuel tank 10 and the fuel vapor discharged from the canister 22 from continuing. The suction force of the canister 22 can be secured by executing as quickly as possible.

  If the result of determination in step 192 is that the coolant temperature THW exceeds the second determination value KTHW + A, the switching valve 26 is turned on, and the canister 22 and the intake passage 32 are brought into communication (step 194). Then, normal purge control of the purge valve 28 is executed (step 196). The ON / OFF state of the switching valve 26 and the purge rate PGR after the determination condition of step 192 is satisfied are indicated by a section D in FIG. At this time, the rich fuel vapor from the fuel tank 10 does not remain in the surge tank 34, or even if it remains, the vapor concentration is suddenly changed by the supply of the fuel vapor from the canister 22. Absent. Therefore, as shown in the section D, the purge rate PGR gradually increases due to the learning accompanying the air-fuel ratio feedback control, and is eventually held at a stable value.

  According to the purge control routine described above, the supply of fuel vapor from the canister 22 to the intake passage 32 is performed not after the stop of the supply of fuel vapor from the fuel tank 10 to the intake passage 32 but after a certain amount of time has elapsed. Thus, it is possible to prevent the air-fuel ratio feedback control from being hindered due to a sudden change in the vapor concentration.

  In the fourth embodiment described above, the “evaporated fuel supply means” according to the fourth aspect of the present invention is realized by the vapor passage 20, the purge valve 28, the switching valve 26, and the ECU 50 that executes the routine of FIG. In the present embodiment, the condition for starting the supply of fuel vapor from the canister 22 is that the cooling water temperature THW rises by the predetermined temperature A after the supply of fuel vapor from the fuel tank 10 is stopped in step 190. However, it is also possible to use other conditions, such as determining that the catalyst temperature rises by a predetermined temperature, that a predetermined time has elapsed, and that the purge rate PGR is 0%.

Embodiment 5.
Hereinafter, a fifth embodiment of the present invention will be described with reference to FIG.
The fuel vapor processing apparatus according to the present embodiment can be realized by causing the ECU 50 to execute the routine of FIG. 10 instead of the routine of FIG. 5 in the second embodiment.

  As described above, the fuel tank 10 is provided with the air inlet 14 so that the inside of the fuel tank 10 is maintained at a substantially atmospheric pressure. However, since the canister 22 provided in the air introduction port 14 has a structure having activated carbon inside, there is a possibility of clogging. When the canister 22 is clogged, the atmosphere cannot be introduced into the fuel tank 10, and therefore, when the fuel vapor is continuously supplied from the fuel tank 10, the pressure in the fuel tank 10 becomes negative. When the pressure in the fuel tank 10 becomes negative, the amount of fuel vapor supplied decreases, and vaporization of light components of the fuel is promoted, resulting in a change in fuel properties in the tank. Therefore, in the present embodiment, the following purge control routine is executed in order to prevent negative pressure in the fuel tank 10.

  FIG. 10 is a flowchart for explaining the flow of purge control executed by the ECU 50 as the control device of the evaporated fuel processing device in the present embodiment. In the routine shown in FIG. 10, first, the engine rotational speed NE is detected based on the output of the rotational speed sensor 46, and compared with the determination value KNE (step 200).

  As a result of the comparison, when the engine speed NE is equal to or smaller than the determination value KNE, the switching valve 26 is maintained in the basic state, that is, the off state (step 202). Further, the purge valve 28 is kept closed (step 204).

  If the engine speed NE exceeds the determination value KNE, in the present embodiment, the tank internal pressure sensor 12 detects the tank internal pressure PTNK and compares it with a predetermined determination value KP (step 206). This determination value KP is set in consideration of the tank internal pressure when a normal canister 22 that is not clogged is provided and the limit tank internal pressure at which the fuel tank 10 is damaged.

  As a result of the determination in step 206, when the tank internal pressure PTNK is larger than the determination value KP, the processing from step 208 to step 216 is executed. Since the processing from step 208 to step 216 is the same as the processing from step 126 to step 134 according to Embodiment 2, the description thereof is omitted here. On the other hand, if the result of determination in step 206 is that the tank internal pressure PTNK is less than or equal to the determination value KP, the switching valve 26 remains off (step 202) and the purge valve 28 remains closed (step 202). 204). That is, the supply of fuel vapor from the fuel tank 10 to the intake passage 32 is not executed.

  According to the purge control routine described above, the supply of fuel vapor from the fuel tank 10 to the intake passage 32 is stopped when the tank internal pressure PTNK of the fuel tank 10 decreases due to clogging of the canister 22 or the like. It is possible to prevent the fuel tank 10 from being damaged due to negative pressure in the tank 10.

  In the fifth embodiment described above, the function of stopping the supply of fuel vapor from the fuel tank 10 when the tank internal pressure PTNK is low is incorporated in the apparatus of the second embodiment. However, the apparatus incorporating the above function is implemented. It is not limited to the apparatus of the form 2 of. That is, the above function can also be incorporated into the device of Embodiment 1, Embodiment 3, or Embodiment 4.

Embodiment 6.
Hereinafter, the fifth embodiment of the present invention will be described with reference to FIGS.
The fuel vapor processing apparatus according to this embodiment is different from that shown in FIG. 11 in that the connection destination of the vapor passage 20 is changed from the upstream portion of the surge tank 34 to the position shown in FIG. This can be realized by executing 12 routines. In addition, in FIG. 11, about the site | part which is common in the above-mentioned Embodiment 2, the same code | symbol is attached | subjected and the overlapping description about them shall be abbreviate | omitted.

  As shown in FIG. 11, the tip of the vapor passage 20 is connected to the intake port 40. The vapor passage 20 downstream of the purge valve 29 is branched into a plurality of branch passages 21, and the branch passages 21 are connected to the intake ports 40 of the respective cylinders. Further, the purge valve 29 according to the present embodiment can control the flow rate of the gas flowing inside each branch passage 21. Therefore, in the evaporative fuel processing apparatus of this embodiment, the fuel vapor is supplied independently for each cylinder, similarly to the fuel injected from the fuel injection valve 44.

  FIG. 12 is a flowchart for explaining the flow of purge control executed by the ECU 50 as the control device of the evaporated fuel processing device in the present embodiment. In the routine shown in FIG. 12, the processing from step 220 to step 226 is the same as the processing from step 120 to step 126 according to the second embodiment, and therefore description thereof is omitted here.

  As a result of the comparison in step 226, when the coolant temperature THW is equal to or lower than the determination value KTHW, the switching valve 26 is maintained in the OFF state which is the basic state (step 228). In the present embodiment, prior to opening the purge valve 29, it is determined whether the fuel injection of the fuel injection valve 44 has been executed for each cylinder (step 230). Whether or not fuel injection has been performed can be determined by whether or not cylinder discrimination has been performed, and cylinder discrimination can be performed by detecting the crank angle. Since the cylinder discrimination method based on the crank angle is known, the description thereof is omitted here. The purge valve 29 remains closed until fuel injection is performed (step 224). After the fuel injection is performed, that is, after the cylinder is determined, the purge valve 29 is opened to the fully opened state sequentially from the cylinder in which the fuel injection is first performed, and the rich fuel vapor in the fuel tank 10 is directly supplied to the intake port 40. (Step 232).

  When cooling water temperature THW exceeds determination value KTHW, switching valve 26 is turned on, and canister 22 and each intake port 40 are brought into communication (step 234). Then, the control of the purge valve 29 is switched from the start-time control in which the drive duty ratio is 100% to the normal purge control (step 236). Thereby, the fuel vapor discharged from the canister 22 is also supplied for each cylinder.

  According to the purge control routine described above, the supply of fuel vapor is started after discrimination of the cylinder in which fuel injection is possible, so that it is possible to prevent unnecessary fuel vapor supply at the initial stage of cranking of the internal combustion engine 30. Thereby, not only can the rich fuel vapor in the fuel tank 10 be used more effectively, but also the unburned HC can be prevented from being exhausted due to the supply of the fuel vapor before ignition.

  In the above-described sixth embodiment, the structure for supplying fuel vapor for each cylinder and the function for supplying fuel vapor after cylinder discrimination are incorporated in the apparatus of the second embodiment. It is not limited to the apparatus of the form 2. That is, the above function can also be incorporated into the device of Embodiment 1, Embodiment 3, Embodiment 4, or Embodiment 5.

Embodiment 7.
Hereinafter, Embodiment 7 of the present invention will be described with reference to FIGS.
The fuel vapor processing apparatus according to the present embodiment can be realized by causing the ECU 50 to execute the routine of FIG. 13 instead of the routine of FIG. 5 in the second embodiment.

  According to the purge control routine of FIG. 5 according to the second embodiment, when the operating internal combustion engine 30 is stopped, the engine speed NE falls below the determination value KNE in step 120, whereby the switching valve 26 Is turned from on to off (step 122), and the purge valve 28 is fully closed (step 124). As a result, the internal combustion engine 30 stops in a state where the vapor passage 20 and the fuel tank 10 communicate with each other. In the next operation, when the condition of step 120 is satisfied, the purge valve 28 is fully opened (step 130), and fuel vapor having a stable concentration is supplied from the fuel tank 10 through the vapor passage 20 to the intake passage 32. The

  However, immediately after the condition of step 120 is satisfied and the purge valve 28 is opened, the thin fuel vapor discharged from the canister 22 flows out into the intake passage 32. This is because the fuel vapor from the canister 22 remains in the vapor passage 20 because the purge valve 28 is closed when the fuel vapor is supplied from the canister 22 at the time of the previous operation stop. In order to further improve the startability of the internal combustion engine 30, it is desired to supply the rich fuel vapor in the fuel tank 10 immediately after the purge valve 28 is opened. Therefore, in this embodiment, immediately after opening the purge valve 28, the purge control routine of FIG. 13 is adopted in order to supply the rich fuel vapor in the fuel tank 10.

  FIG. 13 is a flowchart for explaining the flow of purge control executed by the ECU 50 as the control device of the evaporated fuel processing device in the present embodiment. The purge control according to the present embodiment is characterized by the control content when the internal combustion engine 30 is stopped. The content is the same as the processing up to step 130. Hereinafter, the control unique to the present embodiment will be described mainly.

  In the purge control routine of FIG. 13, when the coolant temperature THW exceeds the determination value KTHW in the determination in step 246, it is determined whether the IG (ignition) switch is on or off (step 252). When the IG switch is turned off, the ECU 50 stops fuel injection and spark ignition, and the internal combustion engine 30 stops. However, since the rotation system of the internal combustion engine 30 continues to rotate for a while due to its inertial force even after the fuel injection and the spark ignition are stopped, the engine speed NE gradually decreases. For this reason, there is a time lag until the engine speed NE decreases after the IG switch is turned off and falls below the determination value KNE in step 240.

  If the result of determination in step 252 is that the IG switch is still on, the switching valve 26 is kept on (step 254), and the purge valve 28 is controlled by normal purge control (step 256). At this time, fuel vapor discharged from the canister 22 is supplied from the canister 22 to the intake passage 32.

  If the result of determination in step 252 is that the IG switch has been turned off, the switching valve 26 is turned off and the fuel tank 10 and the vapor passage 20 are brought into the normal state (step 248). The purge valve 28 is fully opened as in the start-up (step 250). Here, FIG. 14 shows the ON / OFF timing of the switching valve 26 and the purge valve 28 when the routine of FIG. 13 is executed, the ON / OFF timing of the IG switch, the negative pressure in the intake passage 32 and the engine speed NE. It is a figure shown corresponding to this time change. As shown in FIG. 14, while the internal combustion engine 30 continues to rotate even after the IG switch is turned off, the intake passage 32 has a negative pressure corresponding to the engine speed NE due to its pumping effect. Therefore, the gas in the vapor passage 20 is sucked into the intake passage 32, and the fuel vapor in the fuel tank 10 is sucked into the vapor passage 20 by the amount sucked into the intake passage 32 from the vapor passage 20.

  As a result of the determination in step 240, the purge valve 28 is closed when the engine speed NE further decreases and falls below the determination value KNE (step 242). That is, in the present embodiment, as shown in FIG. 14, a time difference TA is provided between the timing for switching the switching valve 26 off and the timing for closing the purge valve 28. As a result, the vapor passage 20 is closed in a state where the rich fuel vapor in the fuel tank 10 is filled therein.

  According to the purge control routine described above, since the operation of the internal combustion engine 30 is stopped in a state where the fuel vapor in the fuel tank 10 is filled in the vapor passage 20, the purge valve 28 is opened at the next start-up. Immediately thereafter, rich fuel vapor can be supplied to the intake passage 32. Therefore, according to the evaporated fuel processing apparatus of the present embodiment, the startability of the internal combustion engine 30 can be further improved as compared with the second embodiment.

  In the seventh embodiment described above, the “evaporated fuel supply means” of the sixth invention is realized by the vapor passage 20, the purge valve 28, the switching valve 26, and the ECU 50 that executes the routine of FIG.

  By the way, in Embodiment 7 mentioned above, the function which stops the internal combustion engine 30 in the state which filled the fuel vapor | steam 10 of the fuel tank 10 in the vapor passage 20 is integrated in the apparatus of Embodiment 2, but the said function Is not limited to the apparatus of the second embodiment. That is, the above function can also be incorporated into the device of Embodiment 3, Embodiment 4, Embodiment 5, or Embodiment 6.

Embodiment 8.
Hereinafter, an eighth embodiment of the present invention will be described with reference to FIG.
The fuel vapor processing apparatus of the present embodiment can be realized by causing the ECU 50 to execute the routine of FIG. 15 instead of the routine of FIG. 5 in the second embodiment.

  According to the seventh embodiment described above, the operation of the internal combustion engine 30 can be stopped in a state where the fuel vapor in the fuel tank 10 is filled in the vapor passage 20. However, depending on the relationship between the volume of the vapor passage 20 and the time from when the switching valve 26 is turned off until the purge valve 28 is closed, fuel vapor larger than the volume of the vapor passage 20 can be sucked out of the fuel tank 10. There is sex. Fuel vapor exceeding the volume of the vapor passage 20 flows into the intake passage 32 and remains in the intake passage 32 even after the internal combustion engine 30 is stopped. At the next start, the fuel vapor remaining in the intake passage 32 is supplied to the internal combustion engine 30 first. The fuel vapor remaining in the intake passage 32 is the fuel in the vapor passage 20. Unlike vapor, its concentration is not stable. Further, when the temperature at the time of stop is low, there is a possibility that the fuel vapor is liquefied in the intake passage 32. In order to stabilize the combustion of the internal combustion engine 30 and improve the startability, it is necessary to supply fuel vapor with a stable concentration. For this purpose, when the internal combustion engine 30 is stopped, the rich fuel vapor remains in the intake passage 32. I do not want to let you. Therefore, in the present embodiment, the purge control routine of FIG. 15 is adopted so that the rich fuel vapor does not remain in the intake passage 32.

  FIG. 15 is a flowchart for explaining a flow of purge control executed by the ECU 50 as a control device of the evaporated fuel processing device in the present embodiment. The purge control of the present embodiment is characterized by the control content after the IG switch is turned off, and the control content before the IG switch is turned off, that is, the processing from step 260 to step 276 is performed in step 240 according to the control routine of FIG. To step 256. Hereinafter, the control unique to the present embodiment will be described mainly.

  In the purge control routine of FIG. 15, if the IG switch is turned off in the determination in step 272, it is next determined whether or not the fuel vapor in the vapor passage 20 has been switched (step 278). The switching of the fuel vapor means switching from a fuel vapor having an unstable concentration discharged from the canister 22 to a fuel vapor having a stable concentration generated in the fuel tank 10. As the switching determination method, for example, the following three methods can be cited.

  The first method is a method of comparing the engine speed NE with a determination value KNEI (where KNE <KNEI). If the engine speed NE falls below the determination value KNEI, it is determined that the inside of the vapor passage 20 has been switched to the fuel vapor from the fuel tank 10. The determination value KNEI can be obtained by experiment.

  The second method is a method of counting the time after the IG switch is turned off with a timer. The timer starts counting when the IG switch is turned off. When the count value TOFF exceeds the determination value KTIME, it is determined that the inside of the vapor passage 20 is switched to the fuel vapor from the fuel tank 10. The determination value KTIME can be obtained by experiment.

  The third method is a method of integrating the purge flow rate QPG after the IG switch is turned off. As described above, the purge flow rate QPG can be obtained by a known method based on the intake pressure PM and the drive duty ratio of the purge valve 28. After the IG switch is turned off, the purge flow rate QPG is integrated, and when the integrated value ΣQPG exceeds the determination value KQPG, it is determined that the vapor passage 20 is switched to the fuel vapor from the fuel tank 10. The determination value KQPG can be obtained by experiment.

  As a result of the determination in step 278, when it is determined that the switching of the fuel vapor in the vapor passage 10 has not been completed yet, the switching valve 26 is in an off state (step 280), and the purge valve 28 is fully opened. (Step 282). During this time, the fuel vapor from the canister 22 remaining in the vapor passage 20 is sucked out into the intake passage 32, and instead the rich fuel vapor in the fuel tank 10 is filled into the vapor passage 20.

  As a result of the determination in step 278, when the completion of switching of the fuel vapor in the vapor passage 20 is recognized, the switching valve 26 remains off (step 262), and the purge valve 28 is closed (step 264). As a result, the vapor passage 20 is closed in a state where the rich fuel vapor in the fuel tank 10 is filled inside without causing the rich fuel vapor in the fuel tank 10 to flow out into the intake passage 32. If it demonstrates using FIG. 14, in this embodiment, the time difference TA between the timing which switches the switching valve 26 to OFF, and the timing which closes the purge valve 28 is required for switching of the fuel vapor in the vapor passage 20. The time is set so that the fuel vapor does not flow into the intake passage 32.

  According to the purge control routine described above, in addition to the effects of the seventh embodiment, the rich fuel vapor in the fuel tank 10 is not allowed to flow out into the intake passage 32. The air can be supplied to the intake passage 32. Although the fuel vapor from the canister 22 remains in the intake passage 32, the concentration of the fuel vapor contained in the purge gas from the canister 22 is extremely lower than that of the fuel vapor in the fuel tank 10. The influence of the remaining fuel vapor on the combustibility of the internal combustion engine 30 is small. Therefore, according to the evaporated fuel processing apparatus of the present embodiment, the startability of the internal combustion engine 30 can be further improved as compared with the seventh embodiment.

  In the above-described eighth embodiment, the “connection switching means” according to the seventh aspect of the invention is realized by the main line 20a, the tank line 20b, the canister line 20c, and the switching valve 26. Further, the “evaporated fuel supply means” of the seventh aspect of the invention is realized by the “connection switching means”, the purge valve 28, and the ECU 50 that executes the routine of FIG.

  By the way, in the above-described eighth embodiment, the function of closing the purge valve 28 when the switching of the fuel vapor in the vapor passage 20 is completed is the same as the thick fuel vapor of the fuel tank 10 in the vapor passage 20 according to the seventh embodiment. Although it is incorporated in the apparatus of the second embodiment in combination with the function of stopping the internal combustion engine 30 in a state where it is charged, the apparatus incorporating the above function is not limited to the apparatus of the second embodiment. That is, the above function can be combined with the function according to the seventh embodiment, and can be incorporated into the device of the third embodiment, the fourth embodiment, the fifth embodiment, or the sixth embodiment.

It is a figure for demonstrating the structure of the evaporative fuel processing apparatus of Embodiment 1 of this invention. It is a flowchart of the purge control routine performed in Embodiment 1 of the present invention. It is a flowchart of the fuel injection time integration routine performed in Embodiment 1 of the present invention. It is a figure for demonstrating the structure of the evaporative fuel processing apparatus of Embodiment 2 of this invention. It is a figure which shows the modification of the evaporative fuel processing apparatus shown to Fig.4 (a). It is a flowchart of the purge control routine performed in Embodiment 2 of the present invention. It is a flowchart of the fuel injection time integration routine performed in Embodiment 2 of the present invention. It is a flowchart of the purge control routine performed in Embodiment 3 of the present invention. It is a flowchart of the purge control routine performed in Embodiment 4 of the present invention. It is a figure which shows the time change of the ON / OFF timing of the switching valve by the purge control routine shown in FIG. 8, and a purge rate. It is a flowchart of the purge control routine performed in Embodiment 5 of this invention. It is a figure for demonstrating the structure of the evaporative fuel processing apparatus of Embodiment 6 of this invention. It is a flowchart of the purge control routine performed in Embodiment 6 of the present invention. It is a flowchart of the purge control routine performed in Embodiment 7 of this invention. FIG. 14 is a diagram illustrating on / off timings of the switching valve and the purge valve according to the purge control routine shown in FIG. 13. It is a flowchart of the purge control routine performed in Embodiment 8 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel tank 14 Atmospheric inlet 22 Canister 20 Vapor passage 20a Main line 20b Tank line 20c Canister line 26 Switching valve 28, 29 Purge valve 30 Internal combustion engine 32 Intake passage 34 Surge tank 44 Fuel injection valve 50 ECU
NE Engine speed THW Cooling water temperature FPG Purge correction coefficient FTNK Vapor concentration coefficient FGPG Vapor concentration learning coefficient PGR Purge rate TAU Fuel injection time TP Basic fuel injection time FAF Air-fuel ratio feedback coefficient PTNK Tank internal pressure

Claims (8)

A fuel tank for storing fuel;
An air inlet for communicating the fuel tank with the outside world and maintaining the inside of the fuel tank from approximately atmospheric pressure to positive pressure;
Evaporative fuel supply means for communicating the fuel tank to the intake passage and supplying the evaporated fuel in the fuel tank to the intake passage when starting the internal combustion engine;
An evaporative fuel processing apparatus for an internal combustion engine, comprising:   2. The internal combustion engine according to claim 1, wherein a canister that adsorbs vaporized fuel generated in the fuel tank is provided at the air introduction port, and the fuel tank communicates with the outside through the canister. Evaporative fuel processing device.   3. The evaporative fuel supply means stops supply of evaporative fuel from the fuel tank to the intake passage when a predetermined operating condition is satisfied after the internal combustion engine is started. Evaporative fuel processing apparatus for internal combustion engine. A canister for adsorbing the evaporated fuel generated in the fuel tank;
4. The internal combustion engine according to claim 3, wherein the evaporated fuel supply means supplies the evaporated fuel discharged from the canister to the front-air intake passage after the supply of the evaporated fuel from the fuel tank to the intake passage is stopped. Evaporative fuel processing equipment for engines.   The evaporative fuel supply means supplies evaporative fuel released from the canister to a front air intake passage after a predetermined time elapses after the supply of evaporated fuel from the fuel tank to the intake passage is stopped. 5. A fuel vapor processing apparatus for an internal combustion engine according to claim 4.   6. The evaporative fuel processing apparatus for an internal combustion engine according to claim 5, wherein the predetermined time is a time until evaporative fuel supplied from the fuel tank to the intake passage is taken into the combustion chamber. The evaporated fuel supply means includes an evaporated fuel passage connected to the intake passage, and a control valve disposed in the evaporated fuel passage,
7. The evaporated fuel processing of an internal combustion engine according to claim 1, wherein when the internal combustion engine is stopped, the control valve is closed with the evaporated fuel passage communicating with the fuel tank. apparatus. The evaporated fuel supply means selectively selects one of an evaporated fuel passage connected to the intake passage, a control valve disposed in the evaporated fuel passage, the canister and the fuel tank as the evaporated fuel passage. Connection switching means for connection,
When the IG switch of the internal combustion engine is turned off, the connection switching means switches the connection to the evaporated fuel passage from the canister to the fuel tank, and the evaporated fuel passage is filled with evaporated fuel generated in the fuel tank. The evaporation of the internal combustion engine according to any one of claims 4 to 6, wherein the control valve is closed in a state where the evaporated fuel passage is communicated with the fuel tank when it is estimated that the evaporation has been performed. Fuel processor.

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